Create a view filter to find node which have no value in a specific field

Question

I'm trying to create an exposed filter for view which allow to find node which have a specific field with no value. It's a field which lists taxonomy terms.

This is not possible with view. When I select to exposed the operator "IS NULL", the filter which is return by view make no sense as you can see on the following images

The filter after I choose this option:

In another issue on stackexchange, someone suggests to use better exposed filter and some people approve. But maybe because the issue was for Drupal 7 or for another type of field, this option is not available with the module for my field.

I create a custom filter which display a checkbox in filter which modify the query to display contents which have this field empty if check.

With EntityQuery, I know it's possible to make a query which return entities with a field empty with the function notExist on the field.

But in the case of the query for view, I have no idea how to indicate I want content which have no connection on this field. I guess I can have this with a subselect in the query but I have no idea how to construct it.

Answer 1

1. Go to the view
2. Add filter for "Tags (field_tags)"
3. Select "Is empty (NULL)" operator

Now only nodes with no tags will show

Answer 2

So, I finally found out how to do it with a left join and verify if it is null or not depending on the value of the checkbox (if checked, should be filled; if not, should be empty). Here is my filter:

<?php

namespace Drupal\my_module\Plugin\views\filter;

use Drupal\Core\Database\Query\Condition;
use Drupal\views\Plugin\views\filter\BooleanOperator;
use Drupal\views\Views;

/**
 * Filters to detect if a content has taxonomy term informed in field_tags.
 *
 * @ingroup views_filter_handlers
 *
 * @ViewsFilter("has_tags_filter")
 */
class HasTagFilter extends BooleanOperator {

  /**
   * Helper function that builds the query.
   */
  public function query() {
    $configuration = [
      'table' => 'node__field_tags',
      'field' => 'entity_id',
      'left_table' => 'node_field_data',
      'left_field' => 'nid',
      'operator' => '=',
    ];
    $join = Views::pluginManager('join')->createInstance('standard', $configuration);
    $this->query->addRelationship('node__field_tags', $join, 'node_field_data');

    if ($this->value == 1) {
      $this->query->addWhere('AND', 'node__field_tags.field_tags_target_id', '', 'IS NOT NULL');
    } else {
      $this->query->addWhere('AND', 'node__field_tags.field_tags_target_id', '', 'IS NULL');
    }
  }
}